Centrifugal pump



May 22, 194.5- G. F. WlsLlcENus Y 2,376,528

GENTRIFUGAL PUMP 2 Sheets-Sheet 1 Filed March 2, 1944 Patented May 22, 1945 'CENTRIHJGAL PUMP George F. Wislicenus, Summit, N. J., asslgnor to Worthington Pump and Machinery Corporation, Harrison, N. J., a corporation of Delaware pplication March 2, 1944, Serial No. 524,711 (ci. s- 108) 3 Claims.

'I'his invention relates to centrifugal Ipumps, compressors and the like,.and more particularly to a rotor and casing structure for machines of the foregoing types.

Casings of the type employed in multistage.

pumping units and the like are divided either "horizontally along their axes or "vertically at right angles to the axes, between the yrespective stages. The horizontally split casing construction has the advantage of `relative ease in dismantling the units. On the other hand, it has been found that in spite of the most extensive efforts the problem of avoiding interstage leakage in horizontally split casings aiiords substantially unsurnfiountable` difficulties. The complete elimination of interstage leakage is almost a necessity in most high pressure pumps, since even a small leakage causes destruction of the surrounding material and thereby an increase of such leakage to an intolerable degree.

The leakage problem has led to the adoption `of the vertical split construction for high pressure and vhigh temperature centrifugal pumps. In this form of design, the stationary part of the pump immediately surrounding the rotor is formed out of ring shaped parts with solid diaphragms reaching inward between the impellers to the wearing diameter. Since these parts can be formed by forging or pressing a nearly one hundred percent leakage-proof construction may be obtained. In dismantling the unit, however, it is necessary to remove the impellers and the stage pieces one by one from theshaft, thus making the process of dismantling a rather lengthy and complicated matter. In order to overcome this diiiiculty. pumps of this type have been incorporated in a unit 'barrel for repair or overhauling. The whole interior pump assembly may be removed from the casing barrel as a unit and replaced by a `completely assembled spare unit. In this way, the time required for dismantling the .pump interior interferes little with the operating schedule or the pump. While this construction has been found very successful, its Very nature makes it rather expensive to build and delicate to assemble.

The hydraulic requirement of using a large number of stages is in many cases in coniiict with order to avoid metallic contact leading to a rapid destruction of the wearing surfaces. Since an increased number of stages will result in a greater shaft bearing span, the hydraulic advantages of the larger number of stages may be partially or totally offset by the necessary increase in shaft diameter resulting from the foregoing consideration of yshaft stiffness.

`A' large diameter shaft passing through the inlet cross-section of a. radial fiow impeller is generally detrimental to the efficiency of the impeller, since it forces an increase in the eye diameter and thereby in the circumferential velocity at which the impeller receives the iiuid. Since an increased number of stages reduces the head per stage and thereby the outside diameter of each impeller, it' is obvious that the increasing shaft diameter has a rapidly growing influence on the form of the impeller and thereby on its hydraulic qualities.

In many practical cases, a point has been reached where because of the foregoing reasons an increase in the number of stages will not result in the usual increase in' eiiiciency unless the corresponding increase in shaft diameter can somehow be avoided. So far the most eiective v way to accomplish this result has been through the use of internal bearings.

Elimination of any stationary diaphragms Winch reach between the individual impellers makes it possible to reduce the axial length required for the respective stages so that the number of stages may be somewhat increased without increasing the shearing span of the shaft.

Accordingly. an object of the present invention is to provide a machine of the type described wherein the construction is such as to avoid the objectionable leakage features characteristic of present day devices.

Another object is to provide a machine of the type. described wherein the casing and the rotor are of such design as to permit axial removal of the rotor intact from the casing by merely de-I the requirement of mechanical reliability of the unit. While most high speed multistage pumping units are operated at speeds above the first critical speed, it is still necessary to keep the static shaft deflection within conservative limits. These deflections' must be lessthan the radial running clearances in the interior of the unit in estl taching one or both end covers of the casing.

Another object is to provide a casing and av rotor of such construction that the running joints in the casing and the rotor maybe machined in one-setting to automatically assure alignment. Another object is to provide a casing structure comprising an assembly of stage pieces or casing rings, in which the exact stage distances may be assured through pre-machining of the individual pieces, and in which the casing lmay be expedi tiously :built in any number of stages by merely assembling and securing together the requisite number of stage pieces.

Another object is to provide a machine or the rotor embodies an impeller structure characterised by a relatively small eye diameter to greatly reduce the circumferential velocity at which the impellers receive the fluid.

Another object is to provide a casing and rotor structure of such design as to eliminate the necessity of stationary diaphragms which reach between the individual impellers to reduce the axial length required for each stage. and in which the necessity of spacer sleeves for mounting the individual impellers on the rotor shaft is completely eliminated, with a consequent reduction in eye diameter.

Another object is to provide a machine of the type described wherein the rotor is of such construction that the fiiud enters through a cylindrical section having the same diameter as the discharge section of the rotor and proceeds to iiow toward the axis of the rotor between rotating side walls, in which the casing contains all the stationary nuid passages to eliminate the necessity of horizontal or vertical separation of the casing, and in which the rotor may be axially removed as a unit from the casing.

A further object is to provide `a machine of the type described wherein the construction is such as to avoid the objectionable features characteristic of horizontally split or vertically split casings of present day construction.

With these and other objects in view, as may appearv from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showinga centrifugal pump of a preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

In the drawings:

Figure 1 is a longitudinal, sectional view of a centrifugal pump in accordance with the present invention.

Figure 2 is a partial sectional view taken along the line 2 2 of Figure l.

Figure 3 is a partial sectional view taken along the line 8 3 of Figure 1.

Figure 4 is a sectional view taken along the line ii-d of Figure l.

Figure 5 is a sectional View taken along the line 5 5 of Figure 1.

Figure 6 is a sectional view of a modified form of casing structure.

Referring more particularly to the drawings, the improved pump shown in Figure 1 comprises a rotor I mounted in a casing I I. The rotor I0 includes a shaft I2 to which impellers are fixediy and permanently attached. Each impeller comprises a side wall or disc I4 lwhich is welded at I to the shaft I2, and the Walls I4 have annular wearing faces i6 of a common diameter. The shaft i2 is undercut at I1, the undercuts comprising circumferential grooves. and the walls I4 are mounted on the uncut shaft portions I8. I

Between the walls I4 are arranged annular rings I9 provided with wearing faces 28 of the same diameter as the walls I4. Outward flow uid impinging vanes 2i xedly relate the rings I8 to their respective walls I4, and the rings are of such shape and arranged in such manner as to co-act with the walls I4 and the faces of the undercuts II to provide fluid passages 22 generally U-shaped in cro-ss-section. The inlet eye of the pump is indicated at 23 and the last-stage eye at 24. lThese eyes respectively communicate with an inlet 25 and a discharge 26.

Each fluid passage 22 extends circumferentially of the axis of the rotor I0, and the legs 21 and 28 of-the fluid passages comprise iiuid inlets and iiuid outlets, respectively. Both the uid inlets and iiuid outlets extend 360 about the rotor and open through the annular perimeter thereof. The vanes 2| are arranged in the legs 28 of the respective fluid passages 22, and the side faces of the walls I4 flare outwardly adjacent the shaft I2 in conformity with the face contours of the undercuts I'I so that the latter comprise continuations of the respective fluid passages. The foregoing rotor structure forms the subject matter of an application for` patent on Rotor flied on even date herewith.

The casing II comprises a series of identically contoured stage pieces or casing rings 28 and two end pieces 30 and 3i, all arranged in end to end relationship and of such diameters as to provide a chamber for the rotor I0. In multistage centrifugal pumps wherein a single volute (as shown in Figure 4) is employed, the stage pieces or sections of the assembled pump are staggered with respect to the one next thereto, (that is, they are preferably displaced 180) to balance radial forces. Annular flanges 32 are provided at one end of the respective pieces 29, which flanges are appropriately tted against annular shoulders 33 on the other ends of the respective pieces. The end piece is also provided with an annular shoulder 34 fitting over the flange 32 on the adjacent piece 29. An annular flange 35 is formed on the end piece 3i for engagement with the shoulder 33 on the adjacent piece 29. Means for iixedly connecting the pieces 29 and the end pieces 30 and 3i into a. unitary structure comprise welded joints 36. All the pieces 29 and the end pieces 30 and 3| are so shaped as to provide circumferential grooves 31 for the welded joints 38.

Internally the pieces 29 and the end pieces 30 and 3| are contoured to provide fluid passages 39 having fluid inlets 39 and uid outlets 40 opening through theinside annular perimeter of the casing I I for communication with the fluid outlet and inlet legs 28 and 21. respectively, in the rotor I0. Thus the assembled pieces 29 and end pieces 30 and 3| provide a casing having a rotor chamber and provided with fluid passages having communication with the rotor chamber. 'I'he inlets 38 and 40 lie in the planes of the legs 2'I and 28, respectively, and the fluid passages 38 are in series communication with the uid passages 22 to provide a continuous fluid passage extending from the inlet 25 to the outlet 26.

Casing rings 4I and 42 are attached to the inner faces ofthe pieces 29 and the end pieces 38 and 3|, as through the medium of locking rings 43. All the casing rings 4I and 42 are of identical inside diameter and lie in the planes of the wearing faces 28 and I6. respectively. It will tlius be seen that the rotor IIl may be axially removed as a unit from the casing II, since the diameter of impeller wearingfaces is at least equal to or greater than the outside diameter Aof the impellers, the inside diameter of the casing rings aard-sas u and `42 being theI smallest diameter of the rotor chamber. In this way any stationary parts reaching between the impellers of the individual stages are completely eliminated.

To the end piece 3U is attached an end cover '4i as by bolts 45, which cover includes an inwardly extending flange d6 appropriately tted inside the end piece 3d and provided with an inturned annular flange di. The cylinder it oi' a stuffing box 49 is welded at 5t) to the inturned iiange di. y

A spacing ring iii is interposed endwise between the end piece di and an end cover d2 at the other end of the casing ii. Bolts di pass through the end cover 52 and the spacer ring di and are threaded into the end piece ti ior connecting these parts into a unitary structure. A casing ring 54 of considerable length extendsinside the end piece 3i and the spacer ring ti at discharge end of the casing and is provided with a ange 55 which is securely clamped between the end piece 3i and the spacer ring iii. wardly extending flange 56 is formed on the end cover 52 and extends inside a sleeve 5l 'bolted at 5d .to a flange 59 on the shaft i2. The sleeve 5l has a wearing surface 60 of considerable area which is arranged m co-active relationship with the inner or wearing face of therlng 5t. The wearingface of the ring `5i is of the same diameter as the wearing faces of the casing rings iii and d2, while the wearing face @t is oi the' same diameter as the wearing faces i6 and 2d. The cylinder 6| of a stuilng box 62 is Welded at t3 to an inwardly extending annular ange tt, at the inner end of the ilange 56.

Both end covers 44 and 52 are provided with extensions indicated fragmentarily at tt which serve as supports for the usual line and thrust bearings (not shown). l

In lieu of building the pump casing from assembled castings, the casing may be cast in one piece. The advantages of building up the casing of individual and small castings resides in the simplification of foundry problems and low pattern costs. .This lconstruction also facilitates cleaning of the fluid passages, and the exact stage distances are assured by pre-machining the individual stage pieces before welding. The individual stage piecesmay be produced in large quantities and kept in stock cleaned, pre-machined, and ready forassembly. Thus casings of any number of stages may be easily built up by conibining the desired number of stock parts by Welding. Final machining of the casing is done' after the casing has been welded together and ap propriately annealed.

Figure 6 illustrates a modification wherein the casing comprises stage pieces or casing rings at arranged end to end in the same manner as the pieces 29. In lieu of welded connections between 'the pieces 6B, the pieces are clamped into a unitary structure by bolts 'l which extend through an end piece 68 at one end of the casing and are threaded into an end piece t@ at the other end of the casing. In Figure 6, the pieces i are provided with engaging annular shoulders 'lil which place and maintain the pieces in coaxial relationship, as is also true of the ilanges 32 and 35 and annular shoulders 33 in the structure of Figure 1. The two end pieces Stand 69 are also shouldered in the same manner as the pieces 66. Internally the pieces 66 and end pieces 68 and 69 may be identical with the pieces 29 and end pieces 30 and 3l. l

Both forms of the device avoid the weakness of reaching between thel individual impellers makes it possible to reduce the length required for each stage so that the number of stages may be some what increased without Aincreasing the bearing span of the rotor shaft. The possibility of fastening the impellers more or less permanently on the shaft makes it very much easier to hold the impellers individually without the use of spacer sleeves. This in turn permits undercutting of the shaft in the region of the impeller inlet and thereby reducing the impeller inlet diameter without an undue reduction oi the average shaft diameter.

The axially removable rotor makes it unnecessary to use the double construction of present day-,barrel pumps since it avoids the principal f disadvantage of the less expensive vertical split dii construction, namely, the tedious piece by piece dismantling of the whole pump including breaky ing of the suction and discharge connections,

which so far has been necessary for removing the rotor from this type of pump.

While the4 drawings show a straightaway or successive arrangement oi the stages of the pump or analogous machine. it is obvious that the principles of the present invention are equally applicable to stage arrangements where the stages are arranged in back-to-baclr relation or in groups disposed in opposed relation, as is the practice in constructing some types of centrifugal pumps.

Obviously, the foregoing f structure oi' both forms of the invention may be easily adapted to compressors, turbines, and the like without de parting from the spirit of the invention.

It will be understood that the invention is not to be limited to the specinc construction or arrangement oi parts shown, but that they may be widely modliied within the invention denned by the claims.

What is claimed is: 1.A In a centrifugal pump oi the multistage type, the combination oi a casing having an inlet and a discharge, said casing being provided with a rotor chamber circular in cross-section and first iiuid passages having rst inlets and first outlets opening into said chamber, a rotor comprising a. shaft having circumferentially extending grooves, walls xed to said shaft between said circumferential grooves, rings lying between said walls and spaced from the faces thereof and the faces of said circumferential grooves to provide second duid passages having second inlets and second outlets respectively communicating with said rst outlets and first inletsin such manner as to connect said first and second fluid passages in series to provide a huid passage leading from said inlet to said discharge, and vanes in said second with respect to the minimum annular contour of said chamber as to be axially removable therefrom intact.

2. The invention claimed in claim 1 wherein said second iiuid passages are generally udhtped in cross-section, and casing rings attached to said casing in the planes of the respective wearing faces.

3. In a centrifugal pump of the multistage type. the combination of a casing having an inlet and a discharge, said casing being provided with a rotor chamber circular in cross-section and rst fluid passages having first inlets and mst outlets opening into said chamber, a rotor comprising a shaft, annular walls iixed to said shaft in co-axial relationship therewith and spaced one from the other, rings lying between said walls and spaced from the faces thereof and the surfaces of said shaft between said'walls to provide second fluid passages having second inlets and second outlets asvasas respectively communicating with said ilrst outlets and first inlets in such manner as to connect said lirst and second fluid passages in series to provide a fluid passage leading from said inlet to said discharge. the surfaces of said shaft between said walls being in fluid passage defining relation-l ship with the faces of said walls, and vanes in said second fluid passages xedly connecting said rings to the respective walls, said walls and said rings having wearing faces of such diameter with respect to the face of said chamber as to provide a running clearance between the rotor and the casing, said rotor having a maximum annular contour such with respect to the minimum annular contour of said chamber as to be axially removable therefrom intact.

GEORGE F. WISLICENUS. 

